The present invention relates to digital X-ray imaging systems, and particularly to techniques for correcting effects of electromagnetic interference (EMI) in image data acquired with such systems.
A number of radiological imaging systems of various designs are known and are presently in use. Such systems generally are based upon generation of X-rays that are directed toward a subject of interest. The X-rays traverse the subject and impact a film or a digital detector. Increasingly, such X-ray systems use digital circuitry for detecting the X-rays, which are attenuated, scattered or absorbed by the intervening structures of the subject. In medical diagnostic contexts, for example, such systems may be used to visualize internal tissues and diagnose patient ailments. In other contexts, parts, baggage, parcels, and other subjects may be imaged to assess their contents and for other purposes.
Basic X-ray systems may be designed for generating projection images only. Such projection images may be presented as a well-known reverse image, although the image data itself is subject to various presentations. In addition to projection X-ray systems, the art now offers fluoroscopy systems, computed tomography systems, and tomosynthesis systems that are based on similar X-ray radiation generation and detection. In computed tomography and tomosynthesis systems, for example, images are computed as slices through the subject based upon various reconstruction techniques applied to multiple collected images.
Various artifacts may be present in radiological system data collected in any one of the foregoing types of systems. Certain types of artifacts are well-known and can be handled, eliminated or corrected in various known ways. However, there are still artifacts that cannot be easily corrected or avoided, at least by known techniques. For example, X-ray systems with digital detectors suffer from artifacts due to the presence of electromagnetic interference (EMI). Sources of EMI may include, for example, various electrical and electronic components that may be used in the vicinity of the X-ray imaging systems, such as radio frequency ablators, magnetic catheter navigations systems, and so forth, to mention only a few. Depending upon the phase, frequency and amplitude of such EMI, artifacts in reconstructed images may generally take the form of darker and lighter parallel rows superimposed on the basic image. Such artifacts are not only distracting, but may impair effective use of the images, such as for diagnosis in a medical context. In particular, such artifacts may make small or more detailed features that would otherwise be visible in the images, difficult to detect and discern. They may also interfere with the effective use of computer assisted techniques, such as computer assisted detection and diagnostic algorithms, segmentation algorithms, and so forth that are becoming increasingly prevalent in medical diagnostic, and part and baggage inspection contexts.
There is a need, therefore, for improved approaches to the elimination of artifacts and noise in radiological image data. There is a particular need for a technique that can address EMI-originating noise in X-ray images.